arm: v7R: Add support for MPU

The Memory Protection Unit(MPU) allows to partition memory into regions
and set individual protection attributes for each region. In absence
of MPU a default map[1] will take effect. Add support for configuring
MPU on Cortex-R, by reusing the existing support for Cortex-M processor.

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0460d/I1002400.html

Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/cpu/armv7m/Makefile b/arch/arm/cpu/armv7m/Makefile
index 6c78d29..baeac93 100644
--- a/arch/arm/cpu/armv7m/Makefile
+++ b/arch/arm/cpu/armv7m/Makefile
@@ -4,5 +4,6 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
 extra-y := start.o
-obj-y += cpu.o cache.o mpu.o
+obj-y += cpu.o cache.o
+obj-$(CONFIG_SYS_ARM_MPU) += mpu.o
 obj-$(CONFIG_SYS_ARCH_TIMER) += systick-timer.o